feat(01-02): add Peewee models, database init, and driver storage

- imptune/db/database.py: deferred SqliteDatabase with WAL + foreign_keys pragmas and init_db()
- imptune/db/models.py: full schema (Client, Driver, Printer, Icon) for phases 1-5
- imptune/storage/driver_store.py: SHA256 content-addressed DriverStore with dedup
- tests/test_db.py: 7 TDD tests covering all db and storage behaviors

tests/test_db.py

@@ -0,0 +1,141 @@
+"""Tests for database initialization and driver storage."""
+import hashlib
+from pathlib import Path
+
+import pytest
+
+
+@pytest.fixture
+def db_env(tmp_path, monkeypatch):
+    """Set up temp DATA_DIR and configure db to use temp paths."""
+    data_dir = tmp_path / "data"
+    data_dir.mkdir()
+    drivers_dir = data_dir / "drivers"
+    drivers_dir.mkdir()
+    db_path = str(data_dir / "imptune.db")
+
+    monkeypatch.setenv("DATA_DIR", str(data_dir))
+
+    import imptune.config as cfg
+    cfg.DATA_DIR = str(data_dir)
+    cfg.DB_PATH = db_path
+    cfg.DRIVERS_DIR = str(drivers_dir)
+
+    # Close and re-init the db with the temp path
+    from imptune.db.database import db
+    if not db.is_closed():
+        db.close()
+
+    return {
+        "data_dir": data_dir,
+        "drivers_dir": drivers_dir,
+        "db_path": db_path,
+    }
+
+
+def test_create_tables(db_env):
+    """init_db() creates all 4 tables in a fresh SQLite file."""
+    from imptune.db.database import db, init_db
+
+    if not db.is_closed():
+        db.close()
+
+    init_db()
+
+    tables = db.get_tables()
+    assert "client" in tables
+    assert "driver" in tables
+    assert "printer" in tables
+    assert "icon" in tables
+
+    db.close()
+
+
+def test_wal_mode(db_env):
+    """After init_db(), PRAGMA journal_mode returns 'wal'."""
+    from imptune.db.database import db, init_db
+
+    if not db.is_closed():
+        db.close()
+
+    init_db()
+
+    cursor = db.execute_sql("PRAGMA journal_mode;")
+    mode = cursor.fetchone()[0]
+    assert mode == "wal"
+
+    db.close()
+
+
+def test_foreign_keys(db_env):
+    """After init_db(), PRAGMA foreign_keys returns 1."""
+    from imptune.db.database import db, init_db
+
+    if not db.is_closed():
+        db.close()
+
+    init_db()
+
+    cursor = db.execute_sql("PRAGMA foreign_keys;")
+    value = cursor.fetchone()[0]
+    assert value == 1
+
+    db.close()
+
+
+def test_idempotent(db_env):
+    """Calling init_db() twice does not raise an error."""
+    from imptune.db.database import db, init_db
+
+    if not db.is_closed():
+        db.close()
+
+    init_db()
+    db.close()
+    init_db()  # second call — must not raise
+
+    db.close()
+
+
+def test_driver_store_save(db_env, tmp_path):
+    """Saving bytes returns their SHA256 hex digest and creates the file."""
+    from imptune.storage.driver_store import DriverStore
+
+    drivers_dir = db_env["drivers_dir"]
+    store = DriverStore(str(drivers_dir))
+
+    data = b"test driver package content"
+    expected_sha256 = hashlib.sha256(data).hexdigest()
+
+    result = store.save(data)
+
+    assert result == expected_sha256
+    assert (drivers_dir / expected_sha256).exists()
+
+
+def test_driver_store_dedup(db_env):
+    """Saving the same bytes twice results in one file on disk."""
+    from imptune.storage.driver_store import DriverStore
+
+    drivers_dir = db_env["drivers_dir"]
+    store = DriverStore(str(drivers_dir))
+
+    data = b"duplicate driver data"
+    store.save(data)
+    store.save(data)
+
+    files = list(drivers_dir.iterdir())
+    assert len(files) == 1
+
+
+def test_driver_store_get_path(db_env):
+    """get_path(sha256) returns the correct file path."""
+    from imptune.storage.driver_store import DriverStore
+
+    drivers_dir = db_env["drivers_dir"]
+    store = DriverStore(str(drivers_dir))
+
+    sha256 = "abcdef1234567890" * 4  # 64 hex chars
+    path = store.get_path(sha256)
+
+    assert path == Path(str(drivers_dir)) / sha256